Warm air furnace structure



Aug. 16, 1938. o. J. KUENHOLD 2,127,177

WARM AIR FURNACE STRUCTURE Original Filed Oct. 7, 1933 4 Sheets-Sheet lZhmentor OTTO J. KUENHOLD Gttornegs A 1938- o. .J. KUENHOLD 2,127,177

WARM AIR FURNACE STRUCTURE Original Filed 001:. '7, 1933 4 Sheets-Sheet2 ZSnventor OTTO J. KUENHOLD Gttornegs Aug. 16, 1938. o. J. KUENHOLDWARM AIR FURNACE STRUCTURE Original Filed Oct. 7, 1933 4 Sheets-Sheet 3with], m

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Aug. 16, 1938; o. J. KuENHoLb 2,127,177

WARM AIR FURNACE STRUCTURE Original Filed Oct. 7, 1933 4 Sheets-Sheet 4Zhwentor OTTO J. KUENHOLD www attorneys Patented Aug. 16, 1938 UNITEDSTATES PATENT OFFICE.

WARM AIR FURNACE STRUCTURE Original application October 7, 1933, SerialNo.

Divided and this application June 8,

1937, Serial No. 147,068

10 Claims.

This invention relates to improvements in furnaces for warm aircirculating systems, and has for its general objects the provision of animproved warm air furnace which has exceptionally high thermalefficiency, free air flow therethrough, equal distribution of heat intoall warm air outlet ducts connected therewith, a neat and compactappearance and maximum safety of operation in use.

A further object of the present invention is the provision of animproved warm air furnace having smoothness and dependability ofoperation, simplicity and economy of production, ease of shipment anderection, and which is capable of manufacture in a large range of sizesfrom a minimum number of foundry patterns.

With the foregoing and other objects in View which will appear as thedescription of the invention proceeds, the invention resides in thecombination and arrangement of parts and in the details of constructionhereinafter described and claimed, it being understood that changes inthe invention as herein disclosed can be made within the scope of whatis claimed without departing from the spirit of the invention.

This application is a division of my copending application Serial No.692,690, filed October 7, 1933.

The present invention will be readily understood from the followingdescription thereof, reference being had to the accompanying drawings inwhich Fig. 1 is a vertical, longitudinal sectional view of a furnaceconstructed in accordance with one embodiment of the invention, the viewbeing in the plane of line Il, Fig. 3; Fig. 2 is a detailcross-sectional view of a portion of one of theside or auxiliary heatconvectors of the furnace, the view being in the plane of the line 2-2,Fig. 5; Fig. 3 is a horizontal sectional view of a furnace constructedin accordance with another embodiment of the present invention, therebeing in this view an unbalanced arrangement of side or auxiliary heatconvectors, three on one side and two on the other side of the centralor main heat convector, whereas in Fig. 1 there is a balancedarrangement of side or auxiliary heat convectors, there being two oneach side of the central or main heat convector; Fig. 4 is a detailvertical sectional View of the vent manifold for the side or auxiliaryheat convectors, the view being in the plane of line 4-4, Fig. 5; Fig. 5is a vertical, transverse sectional view of the furnace, the View beingin the plane of line 55, Fig. 1; and Figs. 6 to 10 inclusive areenlarged sectional views of the draft hood and the explosion reliefmeans associated therewith; Figs. 6 and '7 being vertical sectionalviews on the line 6-7t--1, Fig. 9; Fig. 8 being a vertical sectionalview on the line 8-8, Fig. 9; Fig. 9 being a vertical sectional view onthe line 99, Fig. 8; and Fig. 10 being a vertical sectional View on theline l0li3, Fig. 9.

In its general aspects, the present furnace includes a battery ofgenerally parallel and generally vertically disposed heat convectors 60,10 through which flow the heated products of combustion and between andaround which flow the air to be heated.

In the main and central heat convector are located the fuel burners ofthe furnace, there being three gas burners 5!] in the embodiment of theinvention here shown. Combustion is completed in the liberal sizedcombustion compartment 55 of the main convector and the burned gasesrise or flow upwardly directly to the top of said convector, from whichthey pass laterally into the top cross passages 61 and are distributedthereby into the side or auxiiary heat convectors 10. In these side orauxiliary convectors, the gases are gradually cooled by the upwardlyflowing air surrounding said convectors and as the gases cool theycontract, become heavier and gradually gravitate downwardly towardauxiliary convector outlets at the lower ends thereof. Said outletscommunicate with a common, transversely and generally horizontallydisposed ventmanifold into which-the cooled gases drop and then theypass to and through the manifolds vent outlet into and through thegenerally vertically disposed vent duct 92 by reason of their beingwarmer and lighter than the atmosphere with which the open upper end ofte vent duct 92 communicates. From vent duct 92, the vent gases aredischarged into an open bottom draft hood 100, the top of which istapped by a vent'pipe [06 which conducts said gases to a chimney or thelike.

The circulating air of the heating system enters the furnace through anintake opening in the rear wall of the furnace casing, said air comingfrom the furnace room or the cold air return duct, and being impelledeither by natural gravity circulation or by an air fan or blower 122,Fig. 5. .Upon entering said intake opening the air passes upwardlybetween and around the heat convectors, as shown by the arrows in Fig.1, into the plenum chamber in the, top of the furnace and from thischamber, the heated air passes to the rooms to be heated through warmair ducts in the usual manner.

The heat convectors 60, 10 may be made of pressed or cast metal, in twohalf sections bolted, riveted or otherwise suitably secured together attheir peripheries, or they may be made in one piece cored castings, theformer method being here shown.

The purpose of the forwardly extending inlet to manifold 80 is to tapthe vent gases from the bottom of the side or auxiliary heat convectorsso as to draw off therefrom only the heaviest and therefore the coolestgases. Inasmuch as the vent manifold is located rearwardly of the heatconvectors the upward flow of the air currents between and around theconvectors is not interfered with or disturbed in any way. As shown, thevertically disposed vent duct 92 from the vent manifold outlet islocated close to the rear casing panel of the furnace and specialprovisions are made for conducting the vent gases from the side orauxiliary convectors to the vent manifold outlet in as short and directa course as possible, the cross area of the vent manifold being of extraliberal size, as will be later referred to.

The draft hood I serves the usual functions of a draft hood, the baflleplate I02 thereof deflecting down drafts from the vent duct 92 and byhaving the draft hood open to atmosphere at its lower end, the upwarddraft or suction at the vent manifold, at the lower end of the vent duct92, is limited to that due to the small rise of said vent duct.

The features of the present furnace giving safety against internal gasexplosion will now be described. Notwithstanding the superior efficiencyof gas furnaces employing diving flue circulation of combustionproducts, such as herein disclosed, they have been objected to becausethe lighter-than-air gases, from accidentally opened or extinguishedmain burners and pilots or from burners supposedly but not quite closedby automatic control devices, collect and remain trapped for longperiods of time in the upper fines of the furnace. To overcome thisobjection, I have arranged a direct by-pass passage 1 ID from the top ofthe main or central heat convector, in which the furnace burners arelocated, into the furnace draft hood I00 below the down draft baffle I02thereof, as clearly shown in Figs. 3 and 5.

Referring now to Figs. 6 to 9 inclusive, it will be noted that asuitable closure III is provided for the outlet of this relief passageH0, said closure being pivoted at its upper end on a corrosion-proof pinI03 and being preferably provided on its inner surface with suitablepacking material H2. This relief closure has a lug H3 extending from oneside thereof, see Fig. 9, and to this lug one end of a thermostaticmetal band I I4 is riveted or otherwise suitably secured. When heated byvent gases passing through the draft hood N30, to which gases said bandis exposed, the thermo-metal of the band bends it to the position shownin Fig. 6, with consequent movement by gravity of the relief closure toclosing position, inasmuch as its pivot pin I03 is located inwardly, asshown, from its central gravity plane. Should the vent gases flowingthrough the draft hood cool, either due to turning off or accidentalextinguishment of the furnace burners, the thermostatic band will bendinwardly toward the front of the furnace, as shown. in Fig. '7, and inso doing, will engage an adjustable stud or lift pin I I with consequentpushing of the relief closure partly open, as shown in Fig. 7. Any

lighter-than-air gases which may collect at the top of the mainconvector or at the tops of the cross-connected side convectorstherefore, will be vented from such convectors and will pass into thedraft hood and out through its top outlet to the chimney.

When the furnace burners are again turned on, the hot gases, as soon asthey reach the upper end of the main convector, escape through the nowopen relief passage 1 H1 and in so doing strike the thermo-metal band H4on their way to the chimney. The high heat of said gases promptly causesthe thermo-metal band to bend outwardly,

- as in Fig. 6, permitting the relief closure to close by gravity andsuch closed position of said gate is maintained by the hot vent gasescoming up into the draft hood from the vertical bent duct 92. The reliefclosure, therefore, remains in closed position, out of contact with thelift pin H5, as long as the main burners are on and hot gases areflowing through the draft hood as the result thereof.

The proportions of the parts, especially those of the thermo-metal bandH4, and the adjustment provided at the lift pin H5, may be such that anydesired position of the relief closure relative to the volume of gasbeing burned may be secured. For instance, the relief gate may becracked or opened but slightly when only the pilot burner is on butclosed as soon as any gas is burned by one of the main burners.

It is to be noted that the thermo-metal band H4 is exposed to the highlyheated gases escaping through the relief passage H0 only for very briefperiods, inasmuch as it will close the relief closure before it (theband) can become excessively heated. N 0 work or strain is imposed uponthe thermo-metal band, therefore, except when it is cool or almost cool.When it is heated, it is out of contact with the lift pin H5 andtherefore quite free to assume its normal outwardly bent position inaccordance with the temperature of the vent gases to which it isexposed. The thermo-metal band, for adjustment, etc., is alwaysaccessible through the open bottom of the draft hood, and inasmuch assaid band is constantly under varying temperature, it will effectfrequent movements of the relief closure and thus effectively preventsticking of said closure. It is to be noted also that the relief passageis located below the down draft diverting bafile I02 so that any chimneydown draft occurring while the relief passage is open, as for instancewhile only a pilot flame is burning in the furnace, cannot causeextinguishment of said flame or interference with the venting of thefurnace when cold.

It is to be clearly understood that the function of the above describedautomatic opening of the relief closure while the furnace is cold is notfor the purpose of starting a circulation in the furnace or ofperforming any such function as a by-pass damper to aid in the operationof the furnace, Such aids are not needed in the slightest degree in thepresent furnace and the described operation of the relief passage wouldnot prove effective for such purposes if they were so needed. The extentof opening of the relief passage is sufficient to drain off or vent andthereby prevent any considerable accumulation of explosive gas and airmixtures within the convectors of the furnace and to continuously drainoff or vent gases which originate from leaky valves and the like. Athermostatic safety pilot is provided to prevent long continuedaccidental gas flow into the heat convectors in anyextensive volume.Another function of my-thermostatic relief passage is'to drain offcombustion products when only a. small pilot flame is in operation,which combustion products might otherwise fill the convectors withcarbon dioxide and smother the flame under certain conditions.

The relief passage and its closure have stillanother function and thatis to act as an automatic safety pressure release in case of internalexplosion of gases. Research work upon the present furnace structure byexploding various mixtures of gases placed into the convectors indicatesthat the gravity hung fire door 4! at the front of the furnace acts asan effective means to relieve the pressure of an explosive from the mainconvector to an extent sufficient to prevent damage thereto. The ventmanifold and its outlet and probably other causes seem to preventformation of destructive pressures at the lower ends of the sideconvectors. To similarly relieve pressures due to internal explosionoccurring at the upper ends of the side convectors, the relief passage IIll is provided, being connected directly to the upper end of the mainconvector so as to be able to successfully relieve excessive explosivepressures at the top ends of the side convectors through the top crosspassages BI as well as at the top end of the main convector.

An internal explosion always originates in the vicinity of the mainburner or burners, the pilot burner or burners or the fire door. Such anexplosion will instantly fling the fire door open and the conflagrationand pressure wave, travelling upwardly, promptly flings the reliefclosure IIi wide open, thereby permitting immediate escape of unburnedand burning gases and relieving the compression of the explodingmixture. The sudden force and the rapidity of the explosion are thuseffectively reduced, with consequent reduction of the internal pressureto such a great ex tent that the convectors can'be designed to resistsuch explosive force without the necessity of excessive metal thickness.

Heretofore, explosion relief doors have been so arranged that theexplosion wasvented into the interior of the furnace casing. My methodof venting an explosion into an open bottom draft hood arranged asherein shown and described is a material improvement over anything elseof this kind heretofore attempted- Referring to Fig. 8, it will be notedthat when the relief closure III flies open, it will strike the downdraft baffie I02. Ordinarily, it would dis place or damage this baflle,putting it out of service, and to avoid this, said baffle M32 is hingedat its top and drops by gravity to its normal operating angle as shownin Fig. 10, at which angle it is held by some such stop means as the lugI04. After the explosion, the relief closure I will drop by gravity toits normal working position and the baffle plate I02 will similarly dropdownward. The thermo-metal band I I I will not necessarily be damaged inany way inasmuch as it is fairly thick and swings upwardly out of theway along with the relief closure. The escaping and generally burninggases will strike the outer, downwardly inclined wall of the draft hoodand will be deflected downwardly thereby, thus tending to preventignition of flammable surroundings. The flange I I6 of the reliefpassage conduit serves to securely hold the draft hood from being blownoutwardly by an explosion, such flange being pref erably secured bybolts I I! through the inner wall of the draft hood and the back wall ofthe furnace casing (Fig. 10). When the relief gate is flung open by anexplosion, it causes the baffle plate I02 to close the outlet 35 of thedraft hood into the smoke pipe I06 connected thereto and this tends toprevent spread of the explosion into and hence damage of the vent pipe,inasmuch as the .draft hood outlet will usually be closed a fraction ofa second ahead of the emission of flaming gas from the relief passageIII The described combination of (first), means to prevent or at leastreduce accumulation of explosive gas mixtures within the heat convectorsand (second), means to reduce the severity of an explosion should itoccur, by relieving the pressure at a point approximately half-waybetween the fire door relief means and the vent exits where'the sideconvectors enter manifold Mi constitute important and effective safetyfeatures.

It is desirable also to ventilate the control chamber to preventaccumulation of gases seeping out at joints, valve glands and the like,and this can be done by providing louvered or other suitable openings,as at 25, in the control chamber front panel 24. Inasmuch as this wouldresult in the passage into the furnace room of any gas leakage in thecontrol chamber, I provide said control chamber with an outlet 40communicating directly with the burner compartment 55 located directlyabove said outlet. As the burners, during operation thereof, constantlydraw air through the outlet 40 of the control chamber, continuousventilation of said chamber is effected, the openings 25 in the controlchamber front wall 24 being used for inlet purposes only. Any leaks fromthe gas control manifold system in the control chamber, therefore, willbe vented through the furnace lines to the chimney. When the mainburners are on, the control chamber will be vented to the chimneythrough the vent manifold 8!! and vent duct 92, and when said burnersare off or their flames accidentally extinguished, said control chamberwill be vented to the chimney through the safety by-pass I If] whichwill then be open, as was heretofore pointed out.

Further features of the present invention will be apparent to thoseskilled in the art to which it relates.

What I claim is: a

1. In a furnace, air heating chamber means having a portion adapted tohave products of combustion flow upwardly therethrough and a portionadapted to have products of combustion flow downwardly therethrough,burner means in the first mentioned portion of said chamber means, avent conduit for said products of combustion and communicating with thelower end of said second mentioned portion of said chamber means, adraft hood surrounding the upper end of said vent conduit and having anopening to the atmosphere, by-pass means for establishing communicationbetween said draft hood and the upper end of the first mentioned portionof said chamber means, a down draft baflie in said draft hood fordiverting down draft away from said by-pass means and said vent conduitand to the atmospheric opening of said draft hood, and thermostaticallycontrolled closure means for said by-pass means adapted to open saidby-pass means when said burner means is not in use and to close saidby-pass means when said burner means is in use.

In a furnace, air heating chamber means having a portion adapted to haveproducts of combustion flow upwardly therethrough and a portioncommunicating with the upper end of said first named portion and adaptedto have products of combustion fiow downwardly therethrough, burnermeans in the first mentioned portion of said chamber means, a draft pipefor said products of combustion communicating with the lower end of saidsecond named portion of said chamber means, vent means independent ofsaid draft pipe and having an opening to atmosphere, by-pass means forestablishing communication between said vent means and the upper end ofsaid first named portion of said chamber means, and thermostaticallycontrolled closure means for said by-pass means adapted to open Y saidby-pass means when said burner means is not in use and to close saidby-pass means-when said burner means is in use.

3. In a furnace, air heating chamber means having a portion adapted tohave products of combustion fiow upwardly therethrough and a portioncommunicating with the upper end of said first named portion and adaptedto have products of combustion flow downwardly therethrough, burnermeans in the first mentioned portion of said chamber means, a draft hoodadjacent said furnace and having an opening to atmosphere, an explosionrelief passage for establishing communication between said draft hoodand the upper end of said first named portion of said chamber means, anda gravity closed gate for closing said passage.

4. In a furnace, air heating chamber means having a portion adapted tohave products of combustion fiow upwardly therethrough and a portioncommunicating with the upper end of said first named portion and adaptedto have products of combustion fiow downwardly therethrough, burnermeans in the first mentioned portion of said chamber means, a draft pipefor said products of combustion communicating with the lower end of saidsecond named portion of said chamber means, a draft hood surrounding theupper end of said draft pipe and having an opening to atmosphere, anexplosion relief passage for establishing communication between saiddraft hood and the upper end of said first named portion of said chambermeans, and a gravity closed gate for closing said passage.

5. In a furnace, a chambered main heat convector generally verticallydisposed and adapted to have heated products of combustion flow upwardlytherethrough, a plurality of chambered auxiliary heat convectorsgenerally vertically disposed and communicating with the upper end ofsaid main convector and adapted to have the products of combustion flowdownwardly therethrough, burner means in said main convector, a draftpipe for said products of combustion communicating with the lower end ofsaid auxiliary convectors, a draft hood surrounding the upper end ofsaid draft pipe and having an opening to atmosphere, an explosion reliefpassage for establishing communication between said draft hood and theupper end of said main convector, and a gravity closed gate for closingsaid passage.

In a furnace, a chambered main heat convector generally verticallydisposed and adapted to have heated products of combustion flow upwardlytherethrough, a plurality of chambered auxiliary heat convectorsgenerally vertically disposed alongside said main convector and adaptedto have the products of combustion flow downwardly therethrough, stackmeans communicating with the lower ends of said auxiliary heatconvectors, burner means in said main convector, vent means outside ofand adjacent said furnace, a direct explosion relief passage from thetop of said central convector to said vent means, a normally closedexplosion relief gate in said passage, and passages connecting said mainand auxiliary convectors, said last named passages being of sufficientlylarge cross-section to permit ready relief of explosive pressure fromsaid auxiliary convectors to said relief passage.

7. Furnace construction as in claim 2 and in which said closure meansfor said by-pass means is constructed to operate also as an explosionrelief means.

8. In a furnace, a chambered main heat convector generally verticallydisposed and adapted to have heated products of combustion fiow upwardlytherethrough, a plurality of chambered auxiliary heat convectorsgenerally vertically disposed alongside said main convector and adaptedto have the products of combustion flow downwardly therethrough, burnermeans in said main convector, vent means outside of and adjacent saidfurnace, by-pass means for establishing communication between said ventmeans and the upper end of said main convector, a closure gate for saidby-pass means hinged at the top to close by gravity, and a thermo-metalmember adapted when cold' to change its shape and to engage said gate toopen it.

9. A furnace as in claim 8 in which said thermometal member has oneportion secured to said gate and another portion adapted to engage astationary member when warped by reducing temperatures, and means foradjusting said stationary member to control the point at which saidthermo-metal member opens said gate.

10. A furnace as in claim 3 including means for closing said draft hoodopening to atmosphere by opening of said gate in said relief pas sage byexplosion products passing therethrough.

OTTO J. KUENI-IOLD.

